Process and apparatus for producing a plastic blow-molded part

Abstract

A process for producing a plastic blow-molded part. A plastically deformable plastic parison with a first subregion and an opposite second subregion is placed between a molding element having a projecting region and a mold interacting with the molding element. A positive pressure is generated between the molding element and the first subregion and within the parison, to keep the first subregion at a distance from the molding element and to keep the first and second subregions at a distance from each other. A stretching region of the first subregion is preformed by moving the molding element in relation to an edge region in the direction of the mold and by generating a negative pressure between the projecting region and the stretching region of the first subregion. The subregions are deformed for generating a positive pressure within the parison.

I claim:  
     
       1. A process for producing a plastic blow-molded part, which comprises the steps of: 
       providing a plastically deformable plastic parison having a first subregion and an opposite second subregion;  
       placing the parison between a molding element having at least one projecting region and a mold interacting with the molding element;  
       keeping an edge region of the parison in a fixed position which is adapted to a mold parting region of the plastic blow-molded part to be produced resulting in a fixedly held edge region;  
       generating a positive pressure between the molding element and the first subregion and within the parison for keeping the first subregion at a distance from the molding element and to keep the first subregion and the second subregion at a distance from each other;  
       preforming at least one stretching region of the first subregion by moving the molding element in relation to the fixedly held edge region in a direction of the plastic blow-molded part and by generating a negative pressure between the projecting region and the stretching region of the first subregion to bring at least the stretching region of the first subregion to bear against the projecting region of the molding element; and  
       deforming the first subregion and the second subregion for generating the positive pressure within the parison, the first subregion being brought to bear against the molding element and the second subregion being brought to bear against the mold.  
     
     
       2. The process according to  claim 1 , which comprises preforming the first subregion by generating the negative pressure between the molding element and all of the first subregion to bring the first subregion in its entirety to bear against the molding element. 
     
     
       3. The process according to  claim 1 , which comprises generating a negative pressure between the mold and the second subregion to bring the second subregion to bear against the mold before performing the deforming step. 
     
     
       4. The process according to  claim 1 , which comprises opening the mold by moving at least two of the mold parts forming the mold before performing the generating step, and, after the preforming step, closing the mold by moving the mold parts together to a contour of the plastic blow-molded part to be produced. 
     
     
       5. The process according to  claim 4 , which comprises generating a negative pressure between the mold and the second subregion. 
     
     
       6. The process according to  claim 1 , which comprises introducing a decorative material on a visible side of the plastic blow-molded part to be produced before performing the generating step. 
     
     
       7. The process according to  claim 1 , which comprises providing the plastic parison as a co-extruded parison having at least two layers. 
     
     
       8. The process according to  claim 7 , which comprises providing the parison with at least one reinforced layer and an unreinforced layer as the two layers. 
     
     
       9. The process according to  claim 1 , which comprises forming the molding element as a further mold which interacts with the mold. 
     
     
       10. The process according to  claim 1 , which comprises forming the molding element as a plastic molded part that interacts with the mold. 
     
     
       11. The process according to  claim 10 , which comprises covering the plastic blow-molded part with a decorative material. 
     
     
       12. An apparatus for producing a plastic blow-molded part, comprising: 
       a molding element having at least one projecting region with openings formed therein which can be connected to a negative pressure source;  
       a molding box surrounding said molding element and capable of being subjected to negative pressure, said molding box and said molding element being movable in relation to each other and said molding box having a peripheral edge for securely clamping an edge region of a parison by means of a separate holding device; and  
       a mold disposedopposite said molding element, said mold having mold parts that are movable in such a way that, in a moved-together state, said mold parts can be brought to bear against a contour of the plastic blow-molded part to be produced.  
     
     
       13. The apparatus according to  claim 12 , including contour elements for preforming the parison disposed in said molding box. 
     
     
       14. The apparatus according to  claim 12 , wherein said mold parts of said mold have openings formed therein that can be connected to the negative pressure source. 
     
     
       15. The apparatus according to  claim 12 , wherein said mold is configured at least in certain regions as a jointed band with a number of articulation points. 
     
     
       16. The apparatus according to  claim 12 , wherein said molding element is a further mold which interacts with said mold. 
     
     
       17. The apparatus according to  claim 12 , wherein said molding element is a preformed plastic part that interacts with said mold. 
     
     
       18. The apparatus according to  claim 12 , wherein said mold parts can be brought to bear against said projecting region of said molding element.